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IEEE Antennas and Wireless Propagation Letters
Journal Prestige (SJR): 1.047
Citation Impact (citeScore): 4
Number of Followers: 89  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1536-1225
Published by IEEE Homepage  [228 journals]
  • IEEE Antennas and Wireless Propagation Letters Publication Information

    • Free pre-print version: Loading...

      Pages: C2 - C2
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Phased Array Antenna With Self-Calibration Network and Improved Scanning
           Performance

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      Authors: Yue Xiao;Yong Fan;Yu Jian Cheng;
      Pages: 1226 - 1230
      Abstract: In this letter, a phased array antenna with a self-calibration network and improved scanning performance is proposed. For the online calibration, the phased array antenna requires a self-calibration network, which occupies the space between the antenna elements. Besides, the coupling suppression structure for improving the scanning performance of the phased array also needs to be placed between antenna elements. To place these two structures with different functions at the same time, it is a good method to reuse the self-calibration network as the coupling suppression structure. In this letter, one side of metallic vias of the substrate integrated waveguide cavity to suppress the element coupling is replaced by a coupling microstrip line. Such a hybrid structure can not only realize the online calibration function but also improve the scanning performance of the phased array. Moreover, to reduce the dynamic range of the coupling coefficient between the antenna element and the coupling end of the self-calibration network, reactance regulator blocks are employed on the coupling microstrip line. The coupling coefficient is between −17.2 and −24.5 dB in the operating frequency band from 15 to 17 GHz. With the self-calibration network, the gain of the 8 × 8 patch antenna is increased by 1.95 dB, and the sidelobe level is decreased by about 4.20 dB when scanning at −50° in the E-plane.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Multicompressed-High-Order Modes Dipole Antenna With Wide-Beam and
           High-Gain Radiations in Two Different Bands

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      Authors: Yu Luo;Songjiang Zhao;Ningning Yan;Wenxing An;Kaixue Ma;Fanyi Meng;
      Pages: 1231 - 1235
      Abstract: In this letter, a multicompressed-high-order mode dipole antenna with wide-beam coverage and high-gain radiations in two respective sub-6 GHz bands is proposed. The capacitors and inductors are loaded at the current distribution nulls of the fifth-order mode of the dipole arms. The loading brings the resonant frequencies of the third- and the seventh-order modes closer to the fifth-order mode, and thus achieves wide bandwidth. In addition, the loadings change the current distribution of the third- and the seventh-order modes, and achieve radiation patterns with wide coverage in the lower band and high gain in the higher band. To facilitate fabrication, the capacitors and inductors are replaced by narrow slits and bending lines separately. A prototype of this design is fabricated and measured. The measurement and simulation results are in good agreement. The proposed antenna achieves a wideband of 3.30–5.35 GHz (VSWR < 2) with an omnidirectional radiation pattern in the horizontal plane. In addition, it achieves a ±57° coverage angle over 0 dBi in the lower band and 6.41 dBi peak gain in the higher band in the vertical plane, which can be applied for 5G wireless communication.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Compact and Broadband Circularly Polarized Implantable Antenna for
           Wireless Implantable Medical Devices

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      Authors: Daibin Jing;Hua Li;Xiao Ding;Wei Shao;Shaoqiu Xiao;
      Pages: 1236 - 1240
      Abstract: This letter presents a compact and broadband circularly polarized (CP) implantable antenna for wireless implantable medical devices (WIMDs) in the 2.4 GHz Industrial, Scientific, and Medical band. The proposed antenna consists of a main radiator, a stacked parasitic structure, and a full ground, with its entire dimension of 9.8 × 9.8 × 0.889 mm3. For size reduction, a modified square ring with a mitered cross inside is adopted as the main radiator. By splitting one arm of the mitered cross, the compactness can be further improved while exciting the potential CP radiation. The stacked parasitic structure not only ensures a satisfactory 3 dB axial ratio bandwidth of 28.7%, but also helps to achieve a −10 dB impedance bandwidth of 30%, with a peak realized gain of −24.7 dBi. The antenna was integrated into two types of dummy WIMDs and analyzed in the human phantoms (scalp and heart) to evaluate its device-level performance and robustness. A fabricated prototype was measured in the minced pork, and the measured results agree with the simulated ones.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Dual-Band Beam-Steering Array Antenna With Integration of Reflectarray
           and Phased Array

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      Authors: Mingjiang Teng;Shixing Yu;Na Kou;
      Pages: 1241 - 1245
      Abstract: This letter presents a dual-frequency beam-steering array antenna (DBSA), which integrated a height adjustable reconfigurable reflectarray of C-band and a phased array of X-band. Each antenna element can achieve an arbitrary phase shift value in the range of 0°–360° by controlling the height-adjustable device and digital phase shifter at 5.8 and 10 GHz, respectively. Accordingly, the DBSA can be fed by two sets of feed networks independently, which can simultaneously achieve beam steering of arbitrary angle at dual frequencies. A prototype of 8 × 8 DBSA was designed and fabricated to realized beam scanning in the angle range from −40° to 40° in the XOZ plane at 5.8/10 GHz, respectively. The measured maximum gain of DBSA is 14.4/21 dBi with aperture efficiency of 32.9%/50.6% at 5.8/10 GHz, respectively. The proposed DBSA can be applied in satellite communication to realize air-to-ground and intersatellite communications at the same time.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Miniaturized Wearable Antenna With Five Band-Notched Characteristics for
           Medical Applications

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      Authors: Zitong Zhao;Chao Zhang;Zhonghao Lu;Hongbo Chu;Songmin Chen;Mengyao Liu;Gaosheng Li;
      Pages: 1246 - 1250
      Abstract: In this letter, a miniaturized wearable antenna is proposed, which has five band-notched characteristics. The antenna uses Rogers 5880 as the dielectric substrate, with a thickness of 0.508 mm. Due to its thickness, the antenna can be bent slightly and used in the wearable field. The antenna is fed by a microstrip line with an input impedance of 50 Ω. Through the design of notch structures inside the radiating patch, on either side of the feed line, and on the bottom of the substrate, five notch bands are made possible. More notch bands can be produced by employing a new structure, which produces two notch bands as well as adding metal on the substrate's sides that allows current to be introduced into the notch structures on the bottom of the substrate. Based on this, it is possible to achieve great space utilization and little interaction among notch structures. The proposed antenna has overall size of 30 × 25 × 0.508 mm3 and covers the entire UWB spectrum from 2.56 to 12.7 GHz except notch bands from 2.58 to 3.21 GHz, 4.05 to 4.29 GHz, 5 to 5.64 GHz, 8.60 to 9.05 GHz, and 9.20 to 10.32 GHz. By applying the antenna to the doctor's chest badge, the number of swiping cards by hands can be reduced, which is convenient and avoids bacterial pollution. Thus, the antenna has a useful purpose in the medical development.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Higher Order FD-Padé Scheme for 3-D Parabolic Equation in
           Radio-Wave Propagation

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      Authors: Xiaoping Wu;Zihao Li;Zhixi Liang;Yunliang Long;
      Pages: 1251 - 1255
      Abstract: This letter presents a higher order finite-difference (FD) and Padé approximations method for the three-dimensional (3-D) parabolic equation (PE) to predict radio-wave propagation. This method uses a fourth-order FD approximation of the differential operator in the transverse direction and a higher order Padé approximation of the operator in the propagation direction. The fourth-order FD and higher order Padé (4FDHP) method is then derived. The Leontovich impedance boundary for the 4FDHP method and boundary for the second-order FD and higher order Padé (2FDHP) method are also derived. The important problem of the propagation angle of the different approximations for the 3D-PE is investigated. Simulated results show that the proposed 4FDHP method achieves a larger propagation angle and higher accuracy than those of the 2FDHP method and the Mitchell-Fairweather alternative-direction-implicit method.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Self-Decoupled Dual-Frequency Patch Antennas via Hybrid Coupling Interface
           Technique

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      Authors: Hui Deng;Lei Zhu;
      Pages: 1256 - 1260
      Abstract: This letter presents a novel hybrid coupling interface (HCI) technique to achieve self-decoupling between two dual-frequency patch antennas (DFPAs) for the first time, with no need to introduce external structures. To this end, a decoupling condition based on a detailed network analysis indicates the key to realizing self-decoupling at two operating frequencies simultaneously is that the DFPA must have two independent coupling interfaces (CIs), which is different from the single-band self-decoupling achieved by using mixed coupling in a single CI. Then, an actual DFPA with HCI, composed of a rectangular patch and a short-circuited λ/4 microstrip resonator, is proposed and constructed in a two-element array with another one, which demonstrates that decoupling can be realized by adjusting the radius of the shorting pin conveniently. Finally, experimental results show that the in-band isolation between two antennas can be enhanced beyond 15 dB across two operating frequency ranges of 3.77–3.94 GHz (4.4%) and 4.59–4.72 GHz (2.8%).
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Single-Layer Series-Fed SIW Slot Array Antenna Generating Two Orbital
           Angular Momentum Modes

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      Authors: Ali Vedaee;Alireza Mallahzadeh;
      Pages: 1261 - 1265
      Abstract: A low-profile antenna capable of generating two coaxially propagating orbital angular momentum (OAM) modes is presented. It consists of two series-fed traveling-wave uniform circular arrays of sequentially rotated radiating slots and operates at 10 190 MHz. The smaller and larger radius arrays, with 4 and 8 radiating elements, produce OAM modes with indices lOAM = 0 and +1, respectively. They are designed using a unique simulation-based step-by-step technique and implemented on a single layer of the substrate-integrated waveguide, resulting in a simple structure. The antenna's performance is evaluated using simulations and measurements, with a high agreement between the results. Both modes work in left-hand circular polarization, with the first mode having a gain and axial ratio measured bandwidth of about 5.9 and 3.9%, respectively. In addition, the measured impedance bandwidth for the first and second modes is around 8.2 and 7.9%, correspondingly. Also, the orthogonality bandwidth of two identical antennas set 28 cm apart in front of each other is roughly 4.5%. The antenna's far-field and near-field radiation patterns are also investigated.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Circular-Polarization-Reconfigurable Holographic Leaky-Wave Antenna With
           Fixed-Frequency Beam-Scanning Property

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      Authors: Shanzhe Wang;Zheng Li;Meie Chen;Junhong Wang;
      Pages: 1266 - 1270
      Abstract: A fixed-frequency beam-scanning leaky-wave antenna (LWA) with circular-polarization (CP) reconfigurable property operating in Ka band is developed in this letter. A groove gap waveguide (GGW) structure is adopted for feeding and transmission, and 64 CP patches are excited through the cross-shaped slots etched over the GGW. By switching the conditions between “on” and “off” of the PIN diodes, these exciting slots can act as either transverse slots or longitudinal slots, and hence to realize the transition between left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP). Meanwhile, the fixed-frequency beam-scanning characteristic is achieved by manipulating the hologram, which is controlled by the activation states of diodes. Finally, the presented fabrication is taken into experiment to verify its performance, and an agreement can be observed in the simulated and experimental results. The eventual peak gains reach 13.4 dBic in the LHCP state and 12.1 dBic in the RHCP state, respectively. In addition, a beam-scanning range up to 100° between −50° and 50° is realized with desirable CP reconfigurable performance between LHCP and RHCP.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Pattern-Reconfigurable Sparse Linear Array Synthesis Under Minimum Element
           Spacing Control by Alternating Sequential Quadratic Programming

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      Authors: Lin Li;Rongxiang Guo;Pengfei You;Jingjing Bai;Pei-Yuan Qin;Yanhui Liu;
      Pages: 1271 - 1275
      Abstract: A new method called alternating sequential quadratic programming is proposed to synthesize pattern-reconfigurable sparse linear arrays with minimum element spacing control. The method can find the common element positions and multiple sets of excitations for generating multiple reconfigurable patterns which accurately meet their given upper and lower pattern bounds. In addition, by introducing auxiliary weighting coefficients and collective excitation coefficient vectors and choosing them as optimization variables alternately, the proposed method can appropriately incorporate the minimum element spacing constraint into the pattern synthesis. Synthesized results show that the proposed method can give satisfactory reconfigurable pattern performance but save much more elements compared with some existing methods.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Watson–Watt Direction Finding With Transfer Learning-Based
           Calibration

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      Authors: Gaeron R. Friedrichs;Theodore J. Prince;Mohamed A. Elmansouri;Dejan S. Filipovic;
      Pages: 1276 - 1280
      Abstract: A compression of an entire four-element Watson-Watt direction finding (DF) process, including calibration, into a single neural network based system is introduced. First, WW DF architecture is approximated using neural networks, assuming idealized patterns. Next, the transfer learning (TL) is applied on these patterns to demonstrate that the conventional, often costly look-up-table calibration can be replaced at low cost and overhead. Finally, several neural networks are trained, and their performance is analyzed as a function of what data is used in the TL process, and where it was collected. The proposed DF and calibration procedure is implemented with a four-element array to achieve reduction in the maximum and root mean square DF errors by about 45% and 39%, respectively.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Compact Dual-Band MIMO Antenna With Shared Decoupling Structure for 5G
           Mobile Terminals

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      Authors: Changjiang Deng;Xiaowei Cao;Donghao Li;Weihua Yu;
      Pages: 1281 - 1285
      Abstract: In this letter, a compact dual-band multiple-input–multiple-output antenna, consisting of four antenna pairs, is presented for fifth-generation mobile terminal applications. Each pair includes two tightly arranged monopoles. By folding the L-shaped monopoles into U-shaped structures, both the 3.5 GHz band and 4.9 GHz band can share the same decoupling inductor. By adding stop-band filter on the monopole, dual-band operation can be provided by a single branch. The size of the dual-band antenna pair is merely 19 × 4 mm2. The measured −6 dB bandwidth can cover 3.4–3.6 GHz and 4.8–5.0 GHz, with port isolation higher than 12 dB. The measured radiation efficiency varies from 41% to 59% in the lower band, and varies from 38% to 62% in the upper band.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Dual-Band Dual-Polarized Slotted-Patch Antenna for In-Band Full-Duplex
           Applications

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      Authors: Tran Hien Bui;Hieu Trung Vu;Son Xuat Ta;Khac Kiem Nguyen;Chien Dao-Ngoc;Nghia Nguyen-Trong;
      Pages: 1286 - 1290
      Abstract: This letter presents a dual-band dual-polarized slotted-patch antenna with high isolation and high gain for in-band full-duplex applications. The antenna consists of a double differential-feed $45^circ$-rotated square patch with four capacitively coupled $Gamma$-probes. The proposed design utilizes the TM10 resonant mode of the patch for the lower resonance, whereas four trapezoidal slots are symmetrically etched on the patch to generate the upper resonance. By examining the feeding locations, the four slots can be excited simultaneously, yielding a high-gain radiation at the upper resonance. A design operating at 2.45/5.25 GHz has been optimized with two dual-band rat-race couplers employed to realize the double differential-fed scheme. The fabricated prototype with a profile of 0.06$lambda _{text{2.45-GHz}}$ yields a measured 10 dB return loss bandwidth of 2.40–2.52 GHz and 5.09–5.41 GHz, an isolation of $ge$44 and 41 dB, a gain of 8.5 and 9.2 dBi, and a cross-polarization level of $le$−32 and −22 dB for the lower and upper bands, respectively.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An Orthogonal Beamforming Network Synthesis Method Based on Complex Givens
           Rotation Matrix

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      Authors: Li Sun;Xu-dong Bai;Shi-gang Zhou;
      Pages: 1291 - 1295
      Abstract: This letter studies the possibility of synthesizing an orthogonal beamforming network (BFN) with an arbitrary number of inputs and outputs and beam-shaping functions. The proposed synthesis approach is based on complex Givens rotation matrices and is realized through the optimized program. First, it is derived that a complex Givens rotation matrix can represent a directional coupler with corresponding power ratio and phase difference. Then, this letter presents a computer-aided program to synthesize BFN that combines matrix cascading techniques and optimization algorithms, achieving beam shaping function. For validating the proposed synthesis approach, an example of an orthogonal 2 × 6 BFN with flat-topped radiation patterns for diversity application is presented. The accuracy and efficiency make the proposed synthesis method beneficial in antenna array systems.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An Evaluated PMCHWT Solution of EM Scattering for Mutimedium Targets With
           Variant Permittivities

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      Authors: Yu-Zhe Luan;Min Zhao;Zi He;Da-Zhi Ding;
      Pages: 1296 - 1300
      Abstract: An evaluated Poggio–Miller–Chang–Harrington–Wu–Tsai (PMCHWT) is formulated in terms of the asymptotic waveform evaluation (AWE) technique to predict the scattering characteristics of multimedium targets. At first the uncertain dielectric constant can vary within a certain range by setting it as the permittivity variable. Then the evaluated PMCHWT is constructed with these permittivity variables. Noted that the inversion of the impedance matrix is needed only once and the moment matching technique is used in the process of recursion. Moreover, the high-order derivatives are applied in order to obtain the greater convergence radius. Finally, the impedance matrix, right vector, and the current density are expanded with the Taylor series. The current density is approximated by the reduced order rational Padé function. Compared with the traditional perturbation method, greater radius of convergence can be obtained by using the proposed method. In addition, higher efficiency can be obtained than the general Monte Carlo method.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Short-Time Remote Heart Rate Measurement Based on mmWave FMCW Radar Frame
           Structure

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      Authors: Daeun Jung;Sungpil Cheon;Dongryul Kim;Joonseok Yoon;Byungkwan Kim;
      Pages: 1301 - 1305
      Abstract: This letter presents a novel method to reduce measurement time for remote heart rate measurement using millimeter-wave frequency-modulated continuous wave (FMCW) radar. The proposed method is based on the sampling theory and the frame structure of recent FMCW radar systems. The range displacement from heartbeat is measured by 60 GHz FMCW radar with a fixed frame interval, 50 ms. With additional chirp repetition in each frame, the heartbeat signal can be sampled with increased or decreased interval. By adopting three different sampling rates from a single radar measurement, the resolution of heart rate measurement is improved in a short time, 2.5 s. The proposed method is evaluated with a commercial off-the-shelf FMCW radar system and three different human subjects, for no respiration and natural status. To evaluate the performance of the proposed method, the heart rate result is compared with electrocardiogram (ECG) sensor and conventional signal processing method. The results show that the proposed method estimates the heart rate with lower error and shorter measurement time.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Comparison of Evaporation Duct Height Statistics Based on Surface Bulk
           Measurements Over Yongxing Island

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      Authors: Xiaofeng Zhao;Pinglv Yang;Fenghua Zhou;Zeming Zhou;
      Pages: 1306 - 1310
      Abstract: Six-year high-precision surface bulk measurements are used to analyze the evaporation duct height (EDH) distributions over Yongxing Island. Yearly statistics of the EDH computed by the Paulus-Jeske (PJ) model and the Naval Postgraduate School (NPS) model are compared with an existed historical climatology results used in the AREPS tool. The EDH occurrence frequency distributions (OFD) of the PJ and NPS estimations in different atmospheric regimes are also presented. The findings are outlined as follows: first, the mean EDHs for the PJ model and the NPS model are 14.3 and 11.9 m, respectively. Second, the yearly EDH distributions of the PJ estimations are similar to, but with approximately 2 m lower than that of the AREPS climatology. However, the distributions of the NPS estimations are different, with the highest EDHs occurred in April, May, and June of an average height of 14.2 m, compared to that of the PJ estimations occurred in October, November, and December of an average height of 16.3 m. Finally, for all the partitioned atmospheric regimes, there exists a shifted threshold for the OFD comparisons. Above the threshold, the OFDs of the PJ estimations are higher than that of the NPS estimations, and an opposite situation arises below the threshold.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Circular-Polarized Vortex Beams Generation With Orbital Angular Momentum
           Based on a Leaky-Wave Antenna

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      Authors: Qunhao Zhang;Wan Chen;Haifeng Sun;Jiahui Fu;Yulin Zhao;Hao Feng;Kuang Zhang;
      Pages: 1311 - 1315
      Abstract: A circular-polarized vortex beams generation with orbital angular momentum (OAM) based on a leaky-wave antenna (LWA) with substrate integrated waveguide is proposed in this letter. The loop LWA is designed to transmit vortex beams with various OAM modes controlled by the operating frequency. With the frequency change from 11 to 12 GHz, the OAM modes change accordingly. The OAM antenna realizes a low profile by use of the leaky-wave structure. Meanwhile, two transverse slots and one longitudinal slot are utilized to realize circular polarization to improve the mode purity of OAM. Notably, the measured results demonstrate that the gain reaches 7.18 dBi with vortex beams generated by four OAM modes (+2, +1, 0, −1). The axial ratio is good from 11 to 12 GHz, indicating that circular polarization is achieved.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Passive Metasurface for Gain Enhancement of Wide-Angle Millimeter-Wave
           Multibeam Array Antenna

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      Authors: Qiang Sun;Yong-Ling Ban;Xiao-Fei Li;Jun Hu;Zaiping Nie;
      Pages: 1316 - 1320
      Abstract: In this letter, a passive metasurface for gain enhancement of the wide-angle millimeter-wave (mm-wave) multibeam array antenna (MBA) is proposed, and its core includes the wide-angle Huygens’ unit cell and the point-to-point phase compensation (PPC) method. The Huygens’ unit cell can achieve high transmission performance of the TM-wave in the range of ±70°. The PPC is to map all the beams of the MBA onto the phase modulation plane (PMP), and then block the PMP, that is, each beam corresponds to an independent block region, and each block region can adjust the phase of associated beam independently. Based on the proposed metasurface, the application for improving the beam performance of the MBA is implemented. It can realize the gain enhancement in the range of the beam pointing angle from −55° to +57°. The gain difference between the central beam and the edge beam is 2.69 dBi, and the gain enhancement range is 7.53 to 8.04 dBi.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Spatial-Time-Frequency Information Collaborative Learning for Ionosphere
           Clutter Suppression in HFSWR

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      Authors: Xiaowei Ji;Jiaming Li;Linwei Wang;Qiang Yang;
      Pages: 1321 - 1325
      Abstract: Eliminating the ionosphere clutter is particularly important for high-frequency surface wave radar. This letter fills the gap between the growing interests in the application of deep learning network and the new approach of ionosphere clutter suppression. We present a dynamic collaborative learning strategy to simultaneously learn the spatial-time-frequency information of multicomponent radar echoes for suppressing the ionosphere clutter. For capturing the multidimension information, we design a multichannel time-frequency characteristic learning network and a multichannel spatial characteristic learning network (MS) to sufficiently learn the characteristics of multicomponent radar echoes according to the divided regions. The proposed methodology not only suppresses the ionosphere clutter but also preserves the targets from contaminated region after the suppression process. The results presented in the letter allow demonstrating how the proposed methodology outperforms the approaches taken as reference in all the cases under study.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Channel Hardening: A Comparison Between Concentrated and Distributed
           Massive MIMO

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      Authors: Rafael P. Torres;Jesús R. Pérez;Luis Valle;
      Pages: 1326 - 1330
      Abstract: In this letter, a comparative analysis of the hardening effect for concentrated and distributed massive multiple-input–multiple-output channels (C-mMIMO and D-mMIMO, respectively) is presented. The analysis is carried out in two buildings with similar structural characteristics, considering two frequency bands of interest for 5G deployments, 3.5 and 26 GHz; taking into account both experimental data at 3.5 GHz and simulation results obtained in the 26 GHz band using a rigorous and well-tested ray tracing method. Both, measurements and simulations emulated C-mMIMO and D-mMIMO systems in an indoor cell in the framework of a time division duplex (TDD)-orthogonal frequency division multiplexing (TDD-OFDM) system. To quantify the level of hardening that the specific channels under analysis offer in the frequency domain, the standard deviation of the gain of the channels is used, as well as its evolution as the number of active antennas at the base station grows. The results obtained for both mMIMO systems show that a sufficiently high level of hardening occurs in indoor environments to contribute to the reliability of communication systems or sensor networks.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Nonlinear Through-the-Wall Detection Using DORT Applied With LFM Pulses

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      Authors: Kyuho Cha;Hong Soo Park;Sun K. Hong;
      Pages: 1331 - 1335
      Abstract: The detection of visually obstructed small nonlinear targets in a through-the-wall (TTW) environment is difficult because of linear scatterers and strong wall reflections. In this letter, harmonic-based nonlinear TTW detection is introduced as a method to effectively detect small nonlinear targets behind the wall. Nonlinear TTW detection allows for the suppression of linear scatterer responses and wall reflections by detecting only the harmonics generated from nonlinear targets. Here, we apply the decomposition of the time-reversal operator (DORT) for the detection and separation of multiple nonlinear targets behind the wall. DORT extracts the eigenvalues and eigenvectors of nonlinear targets and allows for selective focusing (imaging) of each detected target. In addition, we utilize linear frequency modulated pulses, which allow for the compression gain in the detection processing. To validate the proposed concept, we conducted simulation and measurements of various configurations of nonlinear TTW detection. The results demonstrate that nonlinear targets behind the wall can be effectively detected and located.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Decoupling Design of Quad-Polarization Overlay Antenna Element With a
           Stacked Structure

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      Authors: Shota Takato;Hiroyuki Arai;Young-Chan Moon;Duk-Yong Kim;
      Pages: 1336 - 1340
      Abstract: This letter presents a design to decouple a quad-polarization antenna element without diodes. It consists of a bottom patch for orthogonally polarized elements and an upper patch twisted at 45° for slant polarized elements. The mutual coupling between the two antennas is reduced by the side wall of the upper element and conductor posts to maintain the distance between the two antennas. The posts also function as an electrical shield of the feeding cable to the upper antenna. The simulation results show that at an antenna height of 0.38λ, the proposed antenna can reduce mutual coupling to less than −15 dB. The measurement results match the simulation results.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Circularly Polarized Dual-Frequency MIMO Antenna With Cosecant-Squared
           Radiation Pattern for Ku-Band Applications

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      Authors: M.V.N. Maruti Ayyadevara;Bhavanam S Naga Kishore;Vasuja Devi Midasala;Sreenivasa Reddy Edara;
      Pages: 1341 - 1345
      Abstract: In this letter, the realization of a circularly polarized multiple-input–multiple-output (MIMO) array antenna with a cosecant-squared pattern is presented. The proposed antenna structure consists of microstrip patches with rectangular slots etched from the top. The desired radiation pattern is generated using amplitude tapering obtained by modifying patch widths and slot lengths, based upon the amplitude coefficients of the Woodward–Lawson method for pattern synthesis. A MIMO arrangement with circular polarization is formed by connecting two such arrays excited by two ports. A Z-shaped slot is used to minimize the mutual coupling. Using two shorting pins, the isolation is enhanced and kept above 30 dB. This arrangement offers a small size (52 × 24 × 0.8 mm3), wide bandwidth, and high-gain antenna operating at 13.2 and 16.6 GHz. The antenna operates in a wide bandwidth, from 12.6 to 14.25 GHz, and from 16 to 17.61 GHz, with admirable directional characteristics. The achieved gain is 16.9 and 16.6 dB with a cosecant pattern and low sidelobe level. The analysis of the VSWR, gain, axial ratio, group delay, efficiency, and MIMO performance metrics are also investigated, both in simulation and in experiment.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Wideband Quad-Polarization-Reconfigurable Bidirectional Antenna With a
           Simple Wideband Switchable Feeding Network

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      Authors: Min Liu;Zhen Jun Zhai;Feng Lin;Hou Jun Sun;
      Pages: 1346 - 1350
      Abstract: This letter presents a wideband quad-polarization-reconfigurable bidirectional antenna using a simple wideband switchable feeding network. By cutting a symmetrical fractal slot on the ground, a wideband dual-polarized differential bidirectional circular monopole antenna with high isolation is realized. To achieve reconfigurable quad-polarization diversity, the bidirectional circular monopole antenna is fed by a wideband switchable feeding network, which provides four output states by only using six PIN diodes. For verification, a prototype operating at 1.85 GHz is designed and fabricated. For the two linear polarization states, the measured 10 dB bandwidths are 28.4% and 25.3%, while the measured peak gains are 4.2 and 3.1 dBi, respectively. For the two circular polarization states, the measured bandwidths with 10 dB return loss and 3 dB axial ratio are 26.3% and 17.4%, respectively. The measured peak gains are 2.8 and 2.4 dBi, respectively.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Parasitic Decoupling Structure for Dual-Polarized Patch Antenna Arrays

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      Authors: Mingcong Xie;Xizhang Wei;Yanqun Tang;Dujuan Hu;
      Pages: 1351 - 1355
      Abstract: In this letter, a simple parasitic structure consisting of a microstrip L-section array and a microstrip U-section array is proposed for mutual coupling reduction of dual-polarization (DP) patch antenna array. The additional coupling paths are introduced by the structure in the cohorizontal polarization (CHP) and covertical polarization (CVP) directions of the array, respectively, to offset the original coupling signals. A $1 times 2$ prototype array with the center to center distance of 0.42${lambda }_0$ is fabricated and measured for verification. The isolation between DP array with decoupling structure reaches to 37.5 and 33.6 dB on CHP and CVP at 4.3 GHz and envelope correlation coefficient is less than 0.004. The radiation gain of the antenna is almost not distorted while the total efficiency is increased from 84% to 91%. In comparison with other related works, our scheme has high isolation and high total efficiency with smaller space and lower profile.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Isolation and Bandwidth Improvements of Multimode Single MPA With
           Copolarized Pattern Using Characteristic Modes Analysis

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      Authors: Neng-Wu Liu;Bing-Bing Huang;Lei Zhu;Guang Fu;
      Pages: 1356 - 1360
      Abstract: A low-profile microstrip patch antenna (MPA) with isolation-bandwidth enhancement is proposed via characteristic mode analysis. First, the MPA under different modes is deeply studied. It demonstrates that the unused modes could be suppressed via the loaded pins. Then, by combining the magnetic wall and electrical wall together of two modes via the pins3, the nulls of the electric fields could be shifted to the unexcited port, thus gaining two minimum mutual coupling poles. After that, the length of the radiator is enlarged to move these two poles together for isolation bandwidth improvement in order to reshape the nonbroadside pattern. Finally, our proposed MPA is fabricated and tested. The results illustrate that its 20 dB isolation bandwidth has been widened to about 2.1% ranging from 4.2 to 4.29 GHz. In addition, it still holds the single-layer, single radiator, and low-profile properties.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Measured Reflection and Transmission Properties of Building Materials for
           Indoor THz Communication

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      Authors: Yang Wang;Yueyang Liu;Xi Liao;Yu Shao;Ziming Yu;Guangjian Wang;Xianjin Li;
      Pages: 1361 - 1365
      Abstract: The knowledge of reflection and transmission properties of building materials is crucial for understanding radio propagation and developing efficient channel models in terahertz (THz) indoor wireless communication. In this letter, such fundamental interaction mechanisms for five common building materials at 219–224 GHz are extensively investigated through experimental measurement campaign, including glass, granite, polyvinyl chloride board, ceramic, and wooden board. Measured results indicate that the reflection coefficients gradually decrease with the increasing of incident angle, whereas the transmission coefficients show weaker angle dependence. In particular, we compare the measured results with those at 40–50 GHz and investigate different characteristics of the materials at the two frequency ranges. Furthermore, the complex permittivity is extracted using least squares fitting methods based on measured reflection coefficients. The results presented in this letter can offer guidance to channel modeling at 220 GHz for indoor low-THz communication.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An Extremely Wideband Tightly Coupled Dipole Array With Shared-Aperture
           Configuration

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      Authors: Shaohua Zhang;Yikai Chen;Shiwen Yang;
      Pages: 1366 - 1370
      Abstract: The intent of this letter is to expand the tightly coupled dipole array (TCDA) concept in a shared-aperture configuration for high radiation efficiency and extremely wide bandwidth. Specifically, a high-band TCDA is deployed beneath the aperture of a low-band TCDA. With this configuration, the profile height keeps the same as that of a stand-alone low-band TCDA. It offers a thin λL/13.7 (or 1.7λH) array with 23.2:1 bandwidth for active voltage standing wave ratio (VSWR) < 3, where λL and λH are the wavelengths at the lowest and highest frequencies of the operating frequency band. Although the shared-aperture configuration is profit for low profile and bandwidth extension, it causes cross-band coupling and deteriorates radiation performance. To solve this issue, the low-band TCDA is designed to be electromagnetic transparent to the high-band electromagnetic waves. The two TCDAs become immune to the cross-band interference and operate properly as in their stand-alone cases. An array prototype consisting of a 16 × 16 high-band array and an 8 × 8 low-band array is fabricated and measured. The measured radiation efficiency is demonstrated to be 77% on average across a 23.2:1 bandwidth.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Compact Dual-Band and Dual-Polarized Base Station Antenna With
           Shared-Dipole Elements

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      Authors: Xin-Hao Ding;Jun-Yao Yang;Wen-Wen Yang;Jian-Xin Chen;
      Pages: 1371 - 1375
      Abstract: In this letter, a compact dual-band and dual-polarized base station antenna with the low-band (LB) and high-band (HB) shared-dipole elements is presented. The proposed antenna consists of a LB element and a HB element with an embedded structure. By sharing the arms of the LB antenna dipoles, the antenna planar size is miniaturized greatly. To reduce the mutual effect between the LB and HB antenna elements, the slots on the LB arms are introduced, resulting in baffles on the four sides. And then, the baffles can also be optimized to stabilize the radiation patterns of the HB antenna. The antenna prototype is fabricated and measured for verification. Results show that the antenna can achieve fractional bandwidths of 40.2% for the LB element and 45.5% for the HB element while the in-band return losses are better than 15 dB, covering the frequency range 0.69–1.02 GHz and 1.70–2.71 GHz for 2G/3G/4G applications. Meanwhile, the measured port isolations are larger than 33 and 38 dB for the LB and HB elements, respectively.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Excitation Flexibility of On-Antenna Power Combining

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      Authors: Sirous Bahrami;Dongseop Lee;Wonbin Hong;Ho-Jin Song;
      Pages: 1376 - 1380
      Abstract: In this letter, a design methodology is proposed for on-antenna power combining with flexible input power ratios. Designing multifeed antennas with direct power combining requires weighted driving signals to match the field distribution at the resonant mode of the antenna, imposing serious restrictions on their implementation. To overcome this drawback, we proposed a method to relax the excitation criterion by altering the impedance matching conditions of the multifeed antenna, giving the RF designers a degree of freedom. First, an eigenanalysis method is employed to extract the active impedance values for each port of the antenna. Then, according to a preferred input power distribution, proper impedance matching is built based on the active impedance values. The resulting multifeed antenna resembles the single-feed antenna in terms of the radiation performance with desired driving signals. A series of four-feed slot antennas were fabricated to validate the proposed method. Simulation and measurement results show that under different excitation scenarios the radiation performance of the antenna remains intact, demonstrating the flexibility for on-antenna power combining.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • All-Metal Monopulse Antenna Array in the Ka-Band With a Comparator Network
           Combining Ridge and Groove Gap Waveguides

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      Authors: Miguel Ferrando-Rocher;Jose Ignacio Herranz-Herruzo;Alejandro Valero-Nogueira;Bernardo Bernardo-Clemente;
      Pages: 1381 - 1385
      Abstract: This letter presents an all-metal three-layer monopulse antenna based on gap waveguide technology operating in Ka-band. (specifically from 29 to 31 GHz) for direction-finding applications. This contribution stands out mainly for the simplicity of its single-layer comparator network (layer 1) composed of a combination of ridge and groove gap waveguides. Also, the compactness of the feed network (layer 2) allows for a low-profile monopulse antenna comprising only three aluminum pieces. The antenna is bottom-fed through three ports connected, two of them to the comparator network, and one directly to the corporate-feed network, to achieve one sum ($Sigma$) and two difference patterns ($Delta _{H}$, $Delta _{E}$). Experimental results validate the concept, showing a close agreement with simulations. The measured null depth is close to $-$30 dB in both difference patterns, and the sum pattern achieves 26.9 dBi directivity with a realized radiation efficiency greater than 80$%$.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Design of Ultrawideband RCS Reduction Metasurface Using Space Mapping and
           Phase Cancellation

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      Authors: Pengfei Gu;Zihao Cao;Zi He;Dazhi Ding;
      Pages: 1386 - 1390
      Abstract: An efficient optimizing method of ultrawideband radar cross-section (RCS) reduction metasurface involves unit amplitude differences and mutual coupling effects are proposed in the letter. Multiple unit phase cancellation was used to broaden RCS-reduction bandwidth. The genetic algorithm was utilized to further design and selects the optimal combination from various tiles. To improve the optimization efficiency and accuracy, the space mapping technique was exploited to refine the design process, which involves the interactions of scattering fields among tiles and subarrays in wideband. Meanwhile, the constraint of wide-angle oblique incidences is also considered in wideband low RCS design. An ultrawideband RCS reduction checkboard meatsurface can be accomplished by fast optimization of low-cost coarse model and few parameter mapping courses between fine and coarse model. A 10 dB RCS reduction for HH and VV polarizations under normal and other oblique incidence angles can be achieved from 5 to 40 GHz. Good agreements between simulation and experiment results are obtained.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Reducing Ground Reflection Multipath Errors for Bluetooth Angle-of-Arrival
           Estimation by Combining Independent Antenna Arrays

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      Authors: Martin L. Sollie;Torleiv H. Bryne;Kristoffer Gryte;Tor Arne Johansen;
      Pages: 1391 - 1395
      Abstract: For outdoor navigation using Bluetooth direction finding, elevation angle estimate errors due to ground reflection multipath interference is a significant challenge at low elevation angles. One of the ways to reduce this issue is to increase the vertical dimension of the array. We consider the synchronization of measurements from two independent arrays stacked vertically to achieve the same effect without needing to construct a larger array, allowing hardware modularity using low-cost equipment. The measurement synchronization is itself affected by the multipath, and a method to handle this effect is proposed. Using measurements from a 15 cm × 15 cm array in field experiments, we demonstrate a reduction in elevation error of up to $10^{circ }$ at elevation angles in the $7^{circ }$–$15^{circ }$ range, where the error was largest when using a single array.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Dual-Wideband Dual-Polarized Magnetoelectric Dipole Antenna for Sub-6 GHz
           Applications

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      Authors: Tian Liu;Wen Jian Zhu;Xiao Jian Hu;Liang Hua Ye;Duo-Long Wu;
      Pages: 1396 - 1400
      Abstract: This letter presents a dual-wideband dual-polarized magnetoelectric dipole (ME) antenna, which works at the prominent frequency bands of 1.7–2.7 GHz and 3.3–5.0 GHz in Sub-6 GHz. A cross ME dipole excites dual-polarized radiation, and a cross strip under the cross dipole embeds a notched band from 2.7–3.3 GHz. Furthermore, a cross patch above the crossdipole and a metal baffle around the ground improve the wideband impedance matching and stable the radiation pattern. As a result, a prototype of the proposed antenna is fabricated and measured. The measured results exhibit dual-wideband and dual-polarized characteristics of 1.66–2.6 GHz (44.13%) and 3.12–5.08 GHz (47.8%), 1.74–2.64 GHz (41.09%), and 3.34–5.08 GHz (42.08%), and the realized gains of 7 and 9 dBi for the two ports, respectively. The proposed antenna is state-of-the-art for base-station applications in Sub-6 GHz.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An Efficient Ray Validation Technique for Ray-Tracing in Urban
           Microcellular Environments

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      Authors: Sajjad Hussain;Conor Brennan;
      Pages: 1401 - 1405
      Abstract: Ray-tracing propagation models for urban microcellular environments become time consuming as the validation of higher order of ray interactions presents a significant computational overhead. This letter presents a time efficient ray validation algorithm for ray-tracing models. The model presented in this letter uses a precomputed database of building faces that are completely or partially visible to each face and vertical edge of all the buildings in the radio environment. This database is used to readily validate the ray-segments between the transmitter and receiver. The validation results show considerable time saving over previous models.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • mmWave Channel Stationarity Analysis of V2X Communications in an Urban
           Environment

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      Authors: Fidel Alejandro Rodríguez-Corbo;Leyre Azpilicueta;Mikel Celaya-Echarri;Raed Shubair;Francisco Falcone;
      Pages: 1406 - 1410
      Abstract: Vehicular communication channels are subject to high nonstationarity mainly characterized by the scatterers’ and/or transceivers’ high mobility. In this sense, this letter presents a characterization of the channel quasi-stationarity regions (QSR) in a V2X generic high-dense urban environment at millimeter wave frequencies (28 GHz). Results are extracted from multiple snapshot simulations by means of a three-dimensional ray-launching algorithm inducing the continuous mobility of the vehicles on the scene and validated with an experimental campaign of measurements in the real scenario. The average power delay profile correlation matrix is used as a descriptor of the channel nonstationarity and the mean correlation is outlined for several thresholds. The obtained QSR results are consistent with the related works reported in the literature. Finally, the effects of these QSR in small- and large-scale parameters are assessed as per threshold considerations.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Low-Cost and Low-Profile Sub-Terahertz Luneburg Lens Beamformer on Polymer

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      Authors: Adham Mahmoud;Jorge Ruiz-García;Olivier de Sagazan;Mauro Ettorre;Ronan Sauleau;David González-Ovejero;
      Pages: 1411 - 1415
      Abstract: A Luneburg lens is used to excite a leaky-wave antenna (array of slots) in the sub-terahertz (sub-THz) frequency range. The antenna is built on a 140-μm thick cyclic Olefin copolymer (COC) substrate. The radiating slots (58 × 24 slots) are etched on the polymer by a photolithographic process, for which the gold (Au) layers are first deposited by evaporation on the COC and, then, patterned by chemical etching. No metalized vias or drilling are applied to the substrate. The full system is fed by a standard WR03 waveguide, and it has been fabricated and tested. Experimental results show an input reflection coefficient better than −7 dB over a 25% fractional bandwidth, spanning from 220 to 290 GHz. The radiated beam can be steered in elevation from −80° to −20° over the same band. The antenna efficiency is estimated to be 20% at the center frequency (260 GHz). This solution provides a simple alternative for low-cost and low-profile beam-scanning antennas in the sub-THz range.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Design of Alvarez Beam Scanning Reflectarray With Inversely Proportional
           Focal Length

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      Authors: Mustafa K. Taher Al-Nuaimi;Shi-Long Zhu;William G. Whittow;Rui-Sen Chen;Guan-Long Huang;Abdelhady Mahmoud;
      Pages: 1416 - 1420
      Abstract: In this letter, a beam scanning Alvarez reflectarray (RA) metasurface with its focal length (F) inversely proportional to the phase distribution on the Alvarez RA aperture is presented for ±45° beam scanning coverage and less than 3 dB gain loss. The beam scanning mechanism is based on mechanically tilting the Alvarez RA panel to the desired direction to steer the beam. Compared to a conventional RA where F is directly proportional to the parabolic phase distribution, the proposed Alvarez RA shows a wider 1 and 3 dB gain bandwidth, higher aperture efficiency (AE), and wider scanning range with less than 3 dB gain loss. The proposed RA has adopted an Alvarez phase distribution, which is a summation of two shifted cubic phase profiles. Pancharatnam– Berry (PB) meta-atoms of subwavelength periodicity were utilized to provide the 360° phase range and to enhance the bandwidth of the RA. An Alvarez RA consisting of 38 × 38 PB meta-atoms has been designed, fabricated, and tested for ±45° beam scan coverage with less than 3 dB gain loss. The simulated and measured results show that the gain of the proposed Alvarez RA metasurface is 29.1 dBi at 19.5 GHz, which corresponds to an AE of 44.2%. The 3 dB gain variation of the Alvarez RA is from 15 to 23.4 GHz, which corresponds to a 3 dB gain bandwidth of 43.7%. The 1 dB gain bandwidth was 27.8% from 17.3 to 22.9 GHz.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Wideband and Wide-Angle Switchable Spatial Filter/Shielding With
           Polarization-Independent Response

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      Authors: Zhefei Wang;Jintao Zhang;Jianqiang Hou;Jiajun Huang;Ziru Hou;Mingxin Song;Tayeb A. Denidni;
      Pages: 1421 - 1425
      Abstract: In this letter, an active second-order frequency-selective surface that features a switchable wide pass-band is proposed. Compared to other multilayer feeding structures, only one layer of frequency-selective surface (FSS) is elaborately reconfigured in this design, whose full planar symmetry structure is not destroyed, to achieve the desired all-polarized controlled behavior. The presented design provides good responses under different incident angles and polarizations. The fulfilled structure is composed of three FSS layers and is controlled by semiconductor switches. When the switches are in off-state, the proposed design acts as a high-transmittance second-order filter with a low ripple level, whose −0.5 dB passband width is over 24.4% and minimum insertion loss is only 0.1 dB. By switching the semiconductors to on-state, the unit cells of the top FSS layer are short-connected, which leads to an ultrawideband shielding behavior from 0 to 10 GHz. Moreover, the proposed structure presents consistent responses under 0°–90° rotation polarizations. Both filter and shielding responses can be obtained up to the 60° incidence. Finally, a prototype is fabricated and measured, and the desired wideband, high-efficiency, wide-angle, and polarization-insensitive switchable performances are obtained through equivalent-circuit calculations, numerical simulations, and experimental measurements.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Grating Lobe Suppression Method Based on Convex Relaxation Iterative
           Optimization in Limited-Scanning Planar Array

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      Authors: Feng Zhao;Xiaoyi Pan;Qianpeng Xie;Xiaoming Meng;Shunping Xiao;
      Pages: 1426 - 1430
      Abstract: Grating lobe (GL) suppression in planar-phased array antennas composed of periodic subarrays with large element spacing has attracted a lot of attention. In this letter, a GL suppression method based on convex relaxation iterative optimization was proposed for limited-scanning planar array. Starting from obtaining the modular structure with best radiation performance by tiling irregular subarrays, a convex relaxation iterative optimization method was raised to optimize the position of module center for suppressing the GLs. This strategy not only suppresses the GLs, but also greatly reduces the cost of array. The effectiveness and potential of the proposed method were verified by different numerical experiments.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Low-Profile Dual-Polarized Substrate Integrated Magneto-Electric Dipole
           MIMO Antenna

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      Authors: Mu-Sheng Liang;Ye Zhou;Xue-Song Yang;Pei-Fang Wu;
      Pages: 1431 - 1435
      Abstract: A magneto-electric dipole (MED) multiple-input–multiple-output (MIMO) antenna with low-profile, dual-polarized, and substrate integrated properties is proposed. The antenna element is composed of four fan-shaped patches lying on the radiation plane and four vertical metal vias linking the patches and the ground. Compared with the common MED antennas, the proposed MED antenna element has a lower profile of 0.1λ. Besides, it is fed by microstrip lines via two orthogonal H-shaped slots, resulting in a broad impedance bandwidth of 40% (3–4.5 GHz) and a steady gain in the entire operational band. The ports isolation is higher than 27 dB, the cross-polarization discrimination is higher than 37 dB, and the measured radiation efficiency is greater than 70%. Furthermore, four antenna elements are utilized to form a MIMO antenna, which can obtain better ports isolation characteristics under the condition that the element spacing is half wavelength. Finally, the MIMO antenna is simulated, fabricated and measured. The results verify the rationality of the design.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An Iterative Nonconformal Domain Decomposition Surface Integral Equation
           Method for Scattering Analysis of PEC Objects

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      Authors: Jiangfei Bai;Shuo Cui;Yaoyao Li;Shunchuan Yang;Donglin Su;
      Pages: 1436 - 1440
      Abstract: Domain decomposition methods can effectively solve electromagnetic scattering problems induced by multiscale perfectly electrically conducting (PEC) objects. However, boundary conditions between adjacent subdomains usually need to be carefully treated, especially when nonconformal meshes exist. To mitigate this issue, an iterative nonconformal domain decomposition surface integral equation (IDD-SIE) formulation is proposed. Each subdomain is independently solved with scattering fields generated from other subdomains as additional excitations. The continuity of current densities across touching interfaces is guaranteed by iteratively solving coupled fields among subdomains. Therefore, troublesome boundary transmission conditions can be avoided and nonconformal meshes are intrinsically supported. Numerical results show that the proposed IDD-SIE formulation is accurate and efficient, and has excellent convergent properties in terms of iteration numbers.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Metal-Only Folded Reflectarray Antenna

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      Authors: Lu Guo;Yifeng Chen;Xiaodong Chen;
      Pages: 1441 - 1445
      Abstract: This letter presents a metal-only folded reflectarray antenna, consisting of three components, namely a pyramidal feed horn, a lower reflectarray, and an upper polarizer, which are all made of metal. The lower reflectarray consisting of planar polarization rotation elements focuses the beam and twists the incoming wave polarization perpendicularly so that the reflection wave can pass through the upper polarizer. With the adjustment of geometrical size, four elements with an equal phase interval of 45° are achieved. In addition, along with their mirror counterparts, 3-bit phase shifting elements covering 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° within 9–10.6 GHz can be realized. For validation, a metal-only folded reflectarray with 610 elements is built and tested. Based on experiment results, 1 dB gain bandwidth is 16% while the peak aperture efficiency is 45%. These promising properties together with the low-profile metal-only structure make the proposed design a great candidate for space applications.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Wideband Millimeter-Wave Corrugated Horn at 30–50 GHz Taking Advantage
           of All-Metal 3-D Printing Fabrication

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      Authors: Haoran Kang;Keiko Kaneko;Ryo Sakai;Alvaro Gonzalez;
      Pages: 1446 - 1450
      Abstract: The development of commercial all-metal 3-D printing technology provides a new fabrication method for wideband millimeter-wave corrugated horns up to 50 GHz. Compared with conventional fabrication techniques, such as direct machining, electroforming, or recently developed methods relying on the assembly of platelets, all-metal 3-D printing has advantages of low cost, fast delivery, possibility of mass production, flexibility in fabrication of complicated geometries, and good mechanical robustness. In this letter, we report the development of a wideband millimeter-wave corrugated horn at 30–50 GHz (50% fractional bandwidth) based on commercial all-metal 3-D printing technology. Measurement results reported in this letter show good performance in terms of both return loss and cross polarization.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Wideband High-Efficiency Circularly Polarized Transmitarray With Linearly
           Polarized Feed

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      Authors: Bin Zheng;Yong Fan;Yu Jian Cheng;
      Pages: 1451 - 1455
      Abstract: By using the low-loss element design method, a wideband high-efficiency transmitarray antenna with the linear-to-circular-polarization transformation is presented. The element is composed of a linearly polarized U-slot patch antenna and a circularly polarized single-arm Archimedean spiral antenna, and has the advantages of low insertion loss and good incident angle stability over a wide frequency band. The 0.14-λ0-thick 1613-element transmitarray is fabricated using standard PCB technology, and presents a measured peak gain of 31.8 dBi with the corresponding aperture efficiency of 60.2%. The measured 1 dB gain bandwidth is 15.2% from 18.25 to 21.25 GHz. Simple structure, high performance, and low complexity make it an attractive candidate for the low-cost, high-gain circularly polarized antenna.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Frequency-Reconfigurable Dielectric Resonator Antenna With a Water Layer

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      Authors: Zhe Chen;Hao-Zhan Li;Hang Wong;Wei He;Jian Ren;Tao Yuan;
      Pages: 1456 - 1460
      Abstract: This letter introduces a frequency-reconfigurable dielectric resonator antenna (DRA) with water layer integration. The proposed method is based on the strategy combination of mode reconfiguration and dielectric loading. First, the frequency band of the DRA is reconfigured between the resonant frequencies of the fundamental $TE_{111}^y$ and quasi-$TE_{113}^y$ modes by flowing liquid control of water pumping in and out of the microfluidic cavity. Then, the frequency response of quasi-$TE_{113}^y$ mode is continuously swept by altering the thickness of water layer. For demonstration, the DRA is designed with a solid dielectric material of K9 glass with the permittivity of 6.25 and loaded with a layer of fresh water with the permittivity of 77. Finally, the proposed antenna is fabricated and measured, which performs with a wideband reconfigurability and stable far-field performance corresponding to the different frequency responses.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Dual-Band Transmitter for Wireless Power Transfer to Biomedical Implant
           Applications

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      Authors: Hoang Le-Huu;Chulhun Seo;
      Pages: 1461 - 1465
      Abstract: This letter presents a dual-band transmitter (DB-Tx) for wireless power transfer to biomedical implants. The DB-Tx operates at $text{1.7},text{GHz}$ (LF-band) and $text{2.1},text{GHz}$ (HF-band) to power implantable devices in deep and shallow implantation, respectively. A bipolar concentric loop (BCL) radiating plane is employed to obtain field-focusing characteristics at dual frequencies, and hence enhance the power transfer efficiency (PTE). Furthermore, a wideband implantable receiver (Rx) is implemented to verify DB-Tx's performance. Experimental results show that, by utilizing the DB-Tx, the transmission range can be extended three times in HF-band and 30% in LF-band, compared with the Tx operating at a single frequency band. The Rx can receive power with the PTE of $-text{14.7},$ and $-text{23},text{dB}$ at $text{10},$ and $text{40},text{mm}$ implantation depth, respectively.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Compact Dual-Polarized Endfire Antenna Array for 5G Millimeter-Wave
           Terminal

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      Authors: Yunli Li;Fan Wu;Dingwei Xi;Zhihao Jiang;Chao Yu;Wei Hong;
      Pages: 1466 - 1470
      Abstract: This letter proposes a compact dual-polarized endfire antenna array for 5G millimeter-wave (mmWave) applications. The dual-polarized antenna unit is constructed by an open-ended substrate integrated waveguide (SIW) cavity for vertically polarized (VP) radiation and a broadband electric dipole for horizontally polarized (HP) radiation. By sharing the side walls of two neighboring SIW channels of the VP elements, the substrate integrated coaxial line feeding structure for the HP element is achieved, allowing a compact size of the final antenna array. To extend the bandwidth of the VP element, the quasi-TE11 mode of the cavity and the slot mode of the endfire aperture are adopted. A corresponding linear array with four units is designed and fabricated. The common −10 dB impedance bandwidth covers the range from 24.8 to 29.2 GHz. The maximum gain is 10.0 dBi for both polarizations, with an overlapped scanning coverage ranging from −41.5° to 45.5° at 27 GHz. The proposed design has a compact configuration, and a wide scanning range, which is an alternative for 5G mmWave terminal application.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Metasurface Cloaking Lens Designed by the Ray Insertion Method

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      Authors: Tien-Chen Yang;Yi-Kai Chen;Malcolm Ng Mou Kehn;
      Pages: 1471 - 1475
      Abstract: This letter presents a metasurface cloak with the ability to make regions of any shape and size on the flat lens invisible in the microwave band. The gradient refractive index (GRIN) of the metasurface is designed by the ray insertion method, which enables the ray paths of electromagnetic surface waves to be tailored in a desired fashion. The lens is composed of periodic metallic square patches etched onto a grounded dielectric substrate to synthesize the required GRIN of the metasurface. The design technique is validated by simulations using commercial software, which demonstrate the successful bending of impingent waves according to the prescribed paths and thus achieving the desired cloaking effect. A prototype of the GRIN metasurface cloak was manufactured and measured, yielding results that verify the theoretical predictions.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Low-Profile Lightweight Slot Array With Solar Cells for 5.8 GHz Band

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      Authors: Wenxing An;Kai Han;Yu Luo;Yongqiang Wang;
      Pages: 1476 - 1480
      Abstract: A 4 × 4 slot array antenna with solar cells is presented for the 5.8 GHz band with a light weight and low profile of 0.039λ (λ is 5.8 GHz wavelength in the air). Coplanar waveguide excitation and foam substrate are adopted for a compact and lightweight structure. The measured impedance matching band is from 5.3 to 6 GHz. The gain range is from 13.7 to 16.3 dBi within the pass band. A tested peak gain of 14.8 dBi is achieved for the target band from 5.725 to 5.85 GHz with a unidirectional pattern. The solar cells can cover 72.5% of the total area with an enhanced capacity for photovoltaic power generation.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • A Compact Wideband Quasi-Yagi Antenna for Millimeter-Wave Communication

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      Authors: Yanyun Chen;Jin Shi;Kai Xu;Longlong Lin;Lei Wang;
      Pages: 1481 - 1485
      Abstract: A millimeter-wave (mm-Wave) quasi-Yagi antenna utilizing a pair of back-to-back U-shaped full-wavelength dipoles and a folded shorted stub-loaded half-wavelength strip resonator is proposed. The high impedance of the U-shaped full-wavelength dipole overcomes the mismatching problem when it is close to the reflector, enabling compact size in the endfire direction. Three reflection zeros can be obtained from the full-wavelength dipole, the half-wavelength strip resonator, and the equivalent inductor and capacitor derived from the folded shorted stub. The three reflection zeros and appropriate impedance make the proposed antenna have wide bandwidth. For demonstration, a prototype of 1 × 4 array is designed with the antenna element planar size (without ground) of 0.57λ0 × 0.18λ0 (λ0 is the wavelength in the free space at center frequency), the 10 dB impedance matching bandwidth of 49.7% (24.2–40.2 GHz), and the average gain of 9.12 dBi. The proposed compact wideband antenna array can be a good candidate for 5G mm-Wave wireless application.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • Ultrawide-Angle and Compact Leaky-Wave Antenna Based on Complex Periodic
           Structure

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      Authors: Xi Wang Dai;Chen Ding;Weiliang Yu;Leilei Liu;Guo Qing Luo;
      Pages: 1486 - 1490
      Abstract: A compact antenna with the characteristic of wide-angle frequency beam scanning based on complex periodic structure is proposed. A double gradient spoof surface plasmon polaritons structure is added to the standard microstrip line for reducing the antenna size. The miniaturization of the proposed antenna is analyzed with the method of dispersion curves and electric field distribution. Periodic changes of the groove depth and trapezoidal gradient structure increase the beam scanning angle from backward to forward and suppress the open stopband effect. The proposed structure is printed on the FR-4 substrate with a compact size of 0.23λ0 × 3.71λ0 (λ0 is the wavelength of the lowest operating frequency), and has a working frequency band from 12.5 to 42.5 GHz for |S11| < −10 dB. Meanwhile, a wide beam-scanning angle of 142° (−52° to +90°) and an average gain of 7.9 dBi are obtained by simulation and measurement. The proposed leaky-wave antenna has a potential application in wireless communication system due to its small size, broad frequency band, wide beam scanning angle and low cost.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An LTCC-Based Antenna Array for D-Band Terahertz Communication

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      Authors: Shengnan Zhao;Yizhen Xu;Yuandan Dong;
      Pages: 1491 - 1495
      Abstract: In this letter, a novel patch antenna array with via and slot loading based on low-loss substrate integrated waveguide feeding network is investigated for D-band applications. The radiating patch element is designed with vias and modified geometry for good broadband impedance matching response and high radiation gain. The feeding network provides the same magnitude and in-phase excitation for the radiating elements in the array. To verify the proposed array design, a 4 × 4 array prototype is implemented by low-temperature cofired ceramic fabrication method and tested. The proposed dual resonance concept is validated by the good agreement between the simulated and measured results. The measurement results of the fabricated prototype show that the proposed design can achieve an 12.5% bandwidth with |S11|< −10 dB (150 to 170 GHz) and realize a maximum gain of 16.8 dBi at 166 GHz. With the combined advantages of wideband, low fabrication difficulty, and stable broadside radiation, the proposed array antenna is considered as a promising candidate for future D-band terahertz phased array communication.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
  • An Ultraminiature Circularly Polarized Microstrip Patch Antenna With MIM
           Capacitors

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      Authors: Chunling Chen;
      Pages: 1496 - 1500
      Abstract: In this letter, an ultraminiature circularly polarized micostrip patch antenna is designed using four metal-insulator-metal (MIM) capacitors. First, four lumped capacitors are added to the edge of the conventional microstrip patch antenna to conduct the simulation of the theoretical model for brevity. It is found that the micostrip patch antenna achieves electrically small (ka < 1) when the capacitors are selected carefully. In addition, the axial ratio and the resonance of the antenna can be optimized by the capacitors, which derive an effective method for designing a compact circularly polarized antenna. Thus, four MIM capacitors are applied to replace the lumped capacitors to make the antenna physically realizable. A circularly polarized (CP) electrically small mictostrip patch antenna is designed, fabricated, and measured to justify the effectiveness of the proposed method. The axial ratio bandwidth and the peak gain of the CP (ka = 0.495) prototype achieves 0.88% and 4.25 dBiC, respectively. The size of the proposed antenna is only 0.104λ0 × 0.104λ0.
      PubDate: June 2023
      Issue No: Vol. 22, No. 6 (2023)
       
 
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